Semiconductor device and manufacturing method of the same

ABSTRACT

An insulating film provided between adjacent pixels is referred to as a bank, a partition, a barrier, an embankment or the like, and is provided above a source wiring or a drain wiring for a thin film transistor, or a power supply line. In particular, at an intersection portion of these wirings provided in different layers, a larger step is formed there than in other portions. Even when the insulating film provided between adjacent pixels is formed by a coating method, thin portions are problematically partially formed due to this step and the withstand pressure is reduced. In the present invention, a dummy material is arranged near the large step portion, particularly, around the intersection portion of wirings, so as to alleviate unevenness formed thereover. The upper wiring and the lower wiring are arranged in a misaligned manner so as not to align the end portions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device having a circuitincluding a thin film transistor (also referred to as a TFT) and amanufacturing method thereof. For example, the present invention relatesto electronic devices having, as a part, an electro-optic devicetypified by a liquid crystal display panel or a light-emitting displaydevice having an organic light-emitting element or an inorganiclight-emitting element.

Note that a semiconductor device in this specification means a genericdevice which can operate with use of semi-conductive characteristics andincludes all types of devices such as an electro-optic device, asemiconductor circuit and an electronic device.

2. Description of the Related Art

In recent years, a technology for forming a thin film transistor (TFT)using a semiconductor thin film (a thickness of around severalnanometers to several hundred nanometers) formed over a substrate havingan insulating surface has been attracting attention. Thin filmtransistors are broadly applied to electronic devices such as an IC oran electro-optic device, and are particularly developed as switchingelements for image display devices at a rapid rate.

Light emitting elements, which use organic compounds as a light emitterand are characterized by their thinness, lightweight, fast response, anddirect current low voltage drive, are expected to be applied tonext-generation flat panel displays. Among display devices, ones havinglight emitting elements arranged in matrix have a wide viewing angle andexcellent visibility.

In a light-emitting display device in which thin film transistors arearranged in matrix over a substrate having an insulating surface, convexor concave portions are formed due to a wiring or an electrode in thesurface of the substrate. When an insulating film is formed thereover bya coating method, it is difficult to have an even thickness. Inaddition, a film thickness over the convex portion becomes thin, by acentrifugal force in forming a film by a coating method. There is aproblem in that resistance to pressure is reduced in the convex portionwhose film thickness of the insulating film is thin.

When the film thickness is made thicker to increase the resistance topressure of the insulating film simply, the stress of the wholeinsulating film is increased. Thus, there is a risk of peeling of theinsulating film or a warpage of a substrate.

In addition, a light-emitting display device in which thin filmtransistors are arranged in matrix has a structure described inReference 1, specifically a structure in which an insulating film isprovided between adjacent pixels (Reference 1: Japanese PatentApplication Laid-Open No. 2002-164181).

The insulating film provided between adjacent pixels is referred to as abank, a partition, a barrier, an embankment or the like, and is providedover a source wiring or a drain wiring for a thin film transistor, or apower supply line. Specifically, at an intersection portion of thesewirings provided in different layers, a larger step is formed there thanin other portions.

Even in the case that the insulating film provided between adjacentpixels is formed by a coating method, there is a problem in that thinportions are partially formed due to this step and the resistance topressure is reduced.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above mentionedproblems. It is an object of the present invention to realize a highlyreliable light-emitting device having a highly insulating property or ahighly resistance to pressure.

In the present invention, a dummy material is arranged near the largestep portion, particularly, around the intersection portion of wirings,so as to alleviate the unevenness (convex and concave portion) of theinsulating film formed thereover.

There is a tendency to produce a partial thin portion when an endportion of an upper wiring and an end portion of a lower wiring arealigned. Thus, one feature of the present invention is to arrange theupper wring and the lower wiring in a misaligned manner so as not toalign the end portions. Further, one feature of the present invention isto arrange the upper wiring and the lower wiring such that a line widthof the upper wiring is broader than a line width of the lower portion,so as not to align the end portions of the upper wiring and the lowerwiring.

In particular, when the upper wiring and the lower wiring are arrangedin parallel, seen from the top, it is preferable that a side face of theupper wiring and a side face of the lower wiring are not aligned.

In addition, in forming the lower wiring, the lower′wiring is preferablyformed to have a tapered shape in the cross section and etching ispreferably conducted to make the wiring width thinner. In other words,the lower wiring is formed to have a cross section having a taperedshape and the etching is conducted to make the wiring width thinner.Then, even when the end portions of the upper wiring and the lowerwiring are aligned in the design of mask, the upper wiring and the lowerwiring can be formed so as not to align the end portions thereof informing the lower wiring and the upper wiring actually.

In the coating (at a normal temperature), a solution for an insulatingmaterial whose viscosity is from 10 cp (centipoises) to 60 cp(centipoises) is applied, and dried to obtain an insulating film havingan even thickness even at the step portion.

By the present invention, an insulating property and resistance topressure between two wiring layers (upper wiring and lower wiring)sandwiching an insulating film can be improved drastically.

The above described means are not merely matters of design, but they arematters invented by the present inventors which have manufactured alight-emitting device, displayed an image by the device and made anample study thereof.

A structure of the present invention is a semiconductor devicecomprising: a first wiring, a second wiring and a metal layer over aninsulating surface; a first insulating layer covering the first wiring,the second wiring and the metal layer; an electrode over the firstinsulating layer, wherein the electrode is in contact with the secondwiring; and a second insulating layer covering the electrode, the firstinsulating layer, the first wiring, the second wiring and the metallayer, wherein the first wiring, the second wiring and the metal layerare made of the same material, and wherein the electrode is providedbetween the metal layer and the first wiring.

Further, a structure of the present invention is a semiconductor devicecomprising: a first wiring and a second wiring over an insulatingsurface; a first insulating layer covering the first wiring and thesecond wiring; a first electrode, a second electrode and a metal layerover the first insulating layer, wherein the metal layer is in anelectrically floating state; a second insulating layer covering thefirst insulating layer, the first electrode, the metal layer, the firstwiring and the second wiring; a light-emitting layer over the secondelectrode; a third electrode over the light-emitting layer, wherein thesecond wiring has a same material as the first wiring, and the metallayer is made of the same material as the first electrode, and whereinthe first electrode is provided between the metal layer and the firstwiring.

One feature of the above structure is that a portion in which the secondelectrode, the third electrode and the light-emitting layer areoverlapped, constitutes a light-emitting element.

A light-emitting element includes a layer including an organic compound(hereinafter, an EL layer) exhibiting electroluminescence by beingapplied with electric field, an anode and a cathode. Luminescence froman organic compound includes luminescence generated in returning to aground state from a singlet excited state (fluorescence) andluminescence generated in returning to a ground state from a tripletexcited state (phosphorescence). The present invention can be applied tocases of using either luminescence.

One feature of the above structure is that the second insulating layeris a partition covering a vicinity portion of the second electrode.

One feature of the above structure is that the metal layer is anelectrode which is electrically floating.

Further, one feature of the above structure is that the semiconductordevice has a first thin film transistor having the first wiring as agate electrode, and a second thin film transistor having the secondwiring as a gate electrode.

Further, an amorphous semiconductor film, a semiconductor film includinga crystalline structure, a compound semiconductor film including anamorphous structure, or the like can be appropriately used as a channelforming region of a thin film transistor (also referred to as a TFT).Furthermore, a semi-amorphous semiconductor film (also referred to as amicrocrystalline semiconductor film) can also be used as a channelforming region of the TFT. The semi-amorphous semiconductor film has anintermediate structure between an amorphous structure and a crystalstructure (also including a single crystal structure and a polycrystalstructure), and a third condition that is stable in term of free energy,and includes a crystalline region having a short-range order withlattice distortion.

In addition, one feature of the above structure is that the secondinsulating layer contains a solvent and is formed by applying a solutionfor a material whose viscosity is 10 cp or more and 60 cp or less by acoating method.

In a semiconductor device of the present invention, a protection circuit(such as a protection diode) may be provided for prevention of damagesby electro-static discharge.

Moreover, in the semiconductor device of the present invention, in acase of a light-emitting device in which light-emitting elements arearranged in matrix, a method for driving a screen display of thelight-emitting device is not limited particularly, and a dot-sequentialdriving method, a line-sequential driving method, a frame sequentialdriving method or the like may be used, for example. The line-sequentialdriving method is typically employed, and a time division gray scaledriving method or an area gray scale driving method may be employedappropriately. In addition, a video signal to be inputted into a sourceline of the light-emitting device may be an analog signal or a digitalsignal, and a driver circuit and the like may be designed appropriatelyaccording to the video signal.

Further, light-emitting devices using digital video signals areclassified into ones in which video signals are inputted into a pixel ata constant voltage (CV), and ones in which video signals are inputtedinto a pixel at a constant current (CC). The light-emitting devices inwhich video signals are inputted into a pixel at a constant voltage (CV)are further classified into ones in which a signal is inputted to alight-emitting element at a constant voltage (CVCV), and ones in which asignal is inputted to a light-emitting element at a constant current(CVCC). The light-emitting devices in which video signals are inputtedinto a pixel at a constant current (CC) are classified into ones inwhich a constant voltage is applied to a light-emitting element as asignal (CCCV), and ones in which a constant current is applied to alight-emitting element as a signal (CCCC).

By the present invention, in a case that an insulating film formed by acoating method is used between films, a short circuit between wiringsprovided in different layers is effectively prevented. Therefore, theyield in a manufacturing process of a semiconductor device can beimproved. Moreover, the reliability of the manufactured semiconductordevices can also be increased.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B are a top view and a cross sectional view showing a partof a pixel of a light-emitting device (Embodiment Mode 1);

FIGS. 2A and 2B are a photograph and a schematic view showing a crosssection around a wiring (Embodiment Mode 2);

FIG. 3 is a top view showing a layout of a pixel as one example(Embodiment Mode 2);

FIGS. 4A and 4B are a top view and a cross sectional view showing alayout of a pixel as one example (Embodiment Mode 3);

FIGS. 5A to 5C show manufacturing steps of a light-emitting device(Embodiment Mode 4);

FIGS. 6A to 6D show manufacturing steps of a light-emitting device(Embodiment Mode 4);

FIG. 7 shows a manufacturing step of a light-emitting device (EmbodimentMode 4);

FIGS. 8A and 8B each show a structure of an active matrix type ELdisplay device (Embodiment Mode 5);

FIGS. 9A to 9D each show one example of an electronic device (EmbodimentMode 6);

FIG. 10 shows an example of an electronic device (Embodiment Mode 6);

FIGS. 11A and 11B show a comparative example; and

FIGS. 12A and 12B are a top view and a cross sectional view showing apart of a pixel of a light-emitting device (Embodiment Mode 1).

DETAILED DESCRIPTION OF THE INVENTION

Embodiment Modes of the present invention are described hereinafter. Thepresent invention is not limited to the following description, and it iseasily understood by those skilled in the art that modes and detailsherein disclosed can be modified in various ways without departing fromthe spirit and the scope of the present invention. It should be notedthat the present invention should not be interpreted as being limited tothe description of the embodiment modes to be given below.

Embodiment Mode 1

Embodiment Mode 1 describes an example in which by providing a dummymaterial, a partial thin portion of an insulating film to be formed overthe dummy material is prevented from occurring, with reference to FIGS.1A and 1B.

FIG. 1A is a top view showing a portion of a pixel of a light-emittingdevice, and FIG. 1B is a cross sectional view taken along a chain lineA-B.

Steps for obtaining the structures shown in FIGS. 1A and 1B aredescribed.

A first insulating layer 11 is formed over a glass substrate 10 havingan insulating surface, and a first wiring 12, a second wiring 13 and ametal layer 14 are formed thereover. The metal layer 14 may be aconductive layer as well. The metal layer 14 serves as a dummy material,and can be an electrode which is in an electrically floating state,i.e., a floating electrode. In addition, the first insulating layer alsoserves as a gate insulating film of a thin film transistor. A gateelectrode of the thin film transistor is formed in the same step as thefirst wiring 12, the second wiring 13 and the metal layer 14.

A second insulating layer 15 and a third insulating layer 16 are stackedto cover these wirings and the metal layer.

The second insulating layer 15 and the third insulating layer 16 areselectively etched using a mask to form a contact hole to reach thesecond wiring 13.

Then, a first electrode formed of a metal material is formed. Here, thefirst electrode has a structure in which a titanium layer 17 a and analuminum layer 17 b are stacked. In addition, a source electrode or adrain electrode of the thin film transistor is formed in the same stepas the first electrode.

A second electrode is formed over the third insulating layer 16. Thesecond electrode is electrically connected to the source electrode orthe drain electrode of the thin film transistor.

Then, a fourth insulating layer 18 is formed by a coating method usingan insulating material including a solvent. At this stage, the statesshown in FIGS. 1A and 1B can be obtained.

It is noted that FIG. 1B shows a light-emitting device which is not yetcompleted. A light-emitting layer including at least one of an organiccompound and an inorganic compound 72, and a third electrode 73 arestacked over the fourth insulating layer 18. A cross sectional viewafter forming the third electrode 73 is shown in FIG. 12B. Thelight-emitting element includes the second electrode 71, thelight-emitting layer including at least one of an organic compound andan inorganic compound 72, and the third electrode 73. In particular,there is a risk that a short circuit may occur between an upper endportion of the aluminum layer 17 b and the third electrode 73. In thisembodiment mode, by forming the metal layer 14 serving as a dummymaterial, the fourth insulating film 18 is prevented from beingpartially thinned. Further, FIG. 12A is a top view showing the pixelarea more widely than FIG. 1A. A source wiring 75 is electricallyconnected to a thin film transistor having the first semiconductor layer19 as an active layer. The first semiconductor layer 19 is electricallyconnected to the first electrode through a contact hole, and the firstelectrode is electrically connected to the second wiring 13 through acontact hole. Further, the second wiring 13 serves as a gate electrodewhich overlaps the second semiconductor layer 77 through the secondinsulating layer 15. The second semiconductor layer 77 is electricallyconnected to a power supply line 78 and a connection electrode 76, andthe connection electrode 76 is electrically connected to the secondelectrode 71. Meanwhile, the connection electrode 76, the source wiring75 and the power supply line 78 are made of the same material as thefirst electrode. The fourth insulating film 18 serves as a partitioncovering an end portion of the second electrode 71, and a vicinity ofthe fourth insulating layer 18 is shown by a reference numeral 74 inFIG. 12A. As shown in FIG. 12A, the present invention prevents a filmthickness of the fourth insulating layer 18 from being partially thinnedby providing the metal layer 14 between the first electrode whichoverlaps the second wiring 13 and the vicinity 74 of the fourthinsulating film 18.

In addition, the first wiring 12 also has a function of alleviatingconvex and concave portions of the fourth insulating layer 18. InEmbodiment Mode 1, by placing the first wiring 12 and the metal layer 14at a certain interval so as to surround the first electrode, theunevenness of the fourth insulating layer 18 is alleviated.

The top shape of the metal layer 14 adopts an L-like shape; however,there is no particular limitation on the shape, and plural rectangleshapes may be used.

Embodiment Mode 2

Embodiment Mode 2 describes an example in which an end portion of anupper wiring and an end portion of a lower wiring are not aligned, withreference to FIGS. 2A, 2B and 3.

Actually, a light-emitting device is formed to have a layout in whichthe positions of the end portion of the upper wiring and the end portionof the lower wiring are different, and a photograph of a cross sectionshowing a part thereof is shown in FIG. 2A. A schematic viewcorresponding to FIG. 2A is shown in FIG. 2B.

In FIG. 2B, a gate metal layer 21, a first insulating layer 22, a firsttitanium film 23 a, an aluminum film 23 b, a second titanium film 23 c,and a second insulating layer 24 are provided over a glass substrate 20.A layer including an organic compound and an upper electrode 25 whichconstitute parts of a light-emitting element are formed over the secondinsulating layer 24. It is noted that a lower electrode of thelight-emitting element is not shown in FIG. 2B.

In addition, as a comparative example, a light-emitting element isformed to have a layout in which an end portion of the upper wiring andan end portion of the lower wiring are aligned, and a cross section of apart thereof is shown in FIG. 11A. FIG. 11B is a schematic viewcorresponding to FIG. 11A. In FIG. 11B, a gate metal layer 61, a firstinsulating layer 62, a first titanium layer 63 a, an aluminum film 63 b,a second titanium film 63 c, and a second insulating layer 64 areprovided over a glass substrate 60. A layer including an organiccompound and an upper electrode 65 which form a light-emitting elementis formed over the second insulating layer 64. In FIG. 11B, a lowerelectrode of the light-emitting element is not shown. As shown in FIG.11A, when the end portion of the upper wiring (63 a to 63 c) and the endportion of the lower wiring (a gate metal layer 61) are aligned, thethickness of the second wiring layer 64 becomes small in the upper endportion of the upper wiring. The smallest thickness is about 0.1 μm. Thethickness of the second wiring layer 64 in the region in which the upperwiring is not formed, is about 1 μm. Accordingly, the thickness of thesecond wiring layer 64 is different in parts, and the largest thicknessis ten times as much as the smallest thickness.

On the other hand, as shown in FIG. 2A, in the case that the positionsof the end portion of the upper wiring (23 a to 23 c) and the endportion of the lower wiring (a gate metal layer 21) are different fromeach other, the distance between the upper end portion of the upperwiring and the upper electrode 25 can be increased. The thickness of thesecond insulating layer 24 in the region in which the upper wiring layeris not formed is equal to that of the second insulating layer 64, about1 μm; however, the smallest thickness of the second insulating layer 24can be about 0.2 μm or more.

In addition, an example of a layout of a pixel is shown in FIG. 3.

In FIG. 3, over an insulating surface, a semiconductor layer (the regionsurrounded by a dotted line in FIG. 3) is formed, a gate insulating filmis formed thereover, and first wirings 41 and 42 are formed thereover atthe same time. One interlayer insulating film or two insulating filmsare formed over the first wiring layer, and second wirings 31 and 32 andelectrodes 33 and 34 are formed over the interlayer insulating film atthe same time. It is noted that the electrode 33 is a connectionelectrode for connecting two TFTs. The electrode 34 is connected to oneelectrode of a cathode and an anode of the light-emitting element.

In FIG. 3, intersection portions of the two wirings, i.e., overlappingportions, are seen. The wirings are arranged such that the end portionsof the wirings, i.e., side faces of the wirings are not aligned witheach other. Specifically, as compared with the second wiring 32, thewiring widths of the first wiring layers 41 and 42 are smaller, and thewirings are arranged such that the side face of the second wiring 32 andthe side face of the first wiring 41 are not aligned, and such that theside face of the second wiring 32 and the side face of the first wiring42 are not aligned.

By adopting the layout of the wirings shown in FIG. 3, when aninsulating film is formed over these wirings by a coating method, it ispossible to prevent the insulating film from being partially thinned.Therefore, an insulator (a partition provided between adjacentlight-emitting elements) which is obtained by patterning the insulatingfilm can prevent a short circuit between electrodes.

In addition, this embodiment mode can be freely combined with EmbodimentMode 1.

Embodiment Mode 3

Embodiment Mode 3 describes a pixel structure in which Embodiment Mode 1and Embodiment Mode 2 are combined with reference to FIGS. 4A and 4B.

A top view of one pixel included in a pixel region of a display deviceis shown in FIG. 4A. In FIG. 4A, the pixel includes a thin filmtransistor 51, a thin film transistor 52, a first electrode layer 50, agate wiring layer 53, a source or drain wiring layer 54, a power supplyline 55, and conductive layers 56 a, 56 b, 56 c and 56 d. A source ordrain electrode layer 58 of the thin film transistor 52 is electricallyconnected to the first electrode 50 through a conductive layer 57. Theconductive layer 57 is formed using the same material and in the samestep as the gate wiring layer 53.

The conductive layers 56 a, 56 b, 56 c and 56 d are formed using thesame material and in the same step as the source or drain wiring layer54, and the power supply line 55, and are provided to alleviate adrastic change of the film thickness caused by stacking of the wirings.The conductive layers 56 a, 56 b, 56 c and 56 d are electricallyinsulated from other wirings. In the region in which the gate wiringlayer 53 intersects with the source or drain wiring layer 54 or thepower supply line 55, wiring layers are stacked, and thus, the filmthickness is increased drastically. However, by placing conductivelayers 56 a, 56 b, 56 c and 56 d around the intersection portion, thecoverage of the insulating layer serving as a partition formed thereoveris increased, and thus, formation defects caused by unevenness of thefilm thickness can be prevented. Part of the conductive layer 56 aoverlaps the gate wiring layer 53. In order to prevent an increase of aparasitic capacitance, the conductive layers 56 b, 56 c and 56 d overlapthe gate wiring layer 53 having intervals with each other. Further, aninsulating film serving as a partition is formed so as to cover an endportion of the first electrode layer 50, and a vicinity of theinsulating film serving as the partition is shown by a reference numeral59 in FIG. 4A. FIG. 4B shows a cross sectional view taken along a lineA-B in FIG. 4A. As shown in FIG. 4B, the conductive layer 56 a isprovided between the vicinity 59 of the insulating film serving as thepartition and a gate electrode of the thin film transistor 51 or 52.

In addition, by arranging the wirings such that a side face of theconductive layer formed using the same material in the same step is notaligned with a side face of the gate wiring layer, it is possible toprevent the thickness of the insulating film serving as a partition frombeing partially thinned.

Therefore, productivity is increased and a display device having a highreliability can be manufactured with a favorable yield.

Embodiment Mode 4

Embodiment Mode 4 describes a manufacturing method of an active matrixlight-emitting device with reference to FIGS. 5A to 5C, 6A to 6D and 7.

A base insulating film 611 is formed over a substrate 610. When light isextracted on the substrate 610 side to display an image, alight-emitting glass substrate or quartz substrate may be used as thesubstrate 610. In addition, a light-transmitting plastic substrate whichcan withstand a processing temperature may be used. In addition, whenlight is extracted on a side opposite to the substrate 610 side todisplay an image, a silicon substrate, a metal substrate or a stainlesssteel substrate whose surfaces are each provided with an insulating filmmay be used, besides the above described substrates. Here, a glasssubstrate is used as the substrate 610. It is noted that a refractiveindex of the glass substrate is around 1.55.

As the base insulating film 611, a base film formed of an insulatingfilm such as a silicon oxide film, a silicon nitride film or a siliconoxynitride film is formed. Here, an example of using a single layerstructure for the base film is shown; however, a structure in which twoor more insulating film mentioned above are stacked may be employed. Inaddition, if unevenness of the substrate or diffusion of an impurityfrom the substrate does not cause a problem, it is not essential to forma base insulating film.

Thereafter, a semiconductor layer 612 is formed over the base insulatingfilm. The semiconductor layer 612 is formed by the following method: asemiconductor film with an amorphous structure is formed by a knownmethod (such as a sputtering method, an LPCVD method, or a plasma CVDmethod), and is crystallized by a known crystallization method (such asa laser crystallization method, a thermal crystallization method or athermal crystallization method using a catalyst such as nickel) toobtain a crystalline semiconductor film. The crystalline semiconductorfilm is patterned into a desired shape using a first photomask to obtainthe semiconductor layer 612. It should be noted that if a plasma CVDmethod is used, the base insulating film and the semiconductor film withan amorphous structure can be sequentially stacked without being exposedto air. The semiconductor film is formed to have a thickness of 25 to 80nm (preferably 30 to 70 nm thick). There is no particular limitation onthe material of the crystalline semiconductor film; however, preferably,silicon, silicon germanium (SiGe) alloy or the like may be used.

In addition, a continuous wave laser may be used for crystallizationtreatment of the semiconductor film with an amorphous structure. Whencrystallizing the amorphous semiconductor film, it is preferable thatsecond to fourth harmonics of a fundamental wave be applied by using asolid laser which can oscillate continuously to obtain a crystal with alarge grain diameter. Typically, a second harmonic (532 nm) or a thirdharmonic (355 nm) of an Nd:YVO₄ laser (a fundamental wave, 1064 nm) maybe applied. When a continuous wave laser is used, laser light emittedfrom a continuous wave YVO₄ laser of output of 10 W is converted toharmonic by a nonlinear optical element. There is also a method foremitting a harmonic by putting a YVO₄ crystal and a nonlinear opticalelement in a resonator. Then, the harmonic is preferably formed so as tohave a rectangular or elliptical shape on an irradiated surface by anoptical system and emitted onto an object to be processed. At this time,an energy density of about 0.01 to 100 MW/cm² (preferably 0.1 MW/cm² to10 MW/cm²) is required. The semiconductor film may be irradiated bybeing moved relatively to the laser light at speeds of about 10 to 2000cm/s.

Thereafter, a resist mask is removed. Then, if necessary, a slightamount of an impurity element (boron or phosphorus) is added into thesemiconductor film to control a threshold value of the TFT. Here, an iondoping method in which diborane (B₂H₆) is plasma-excited without massseparation is used.

Then, an oxide film is removed from the surface of the semiconductorlayer by an etchant including hydrofluoric acid, and at the same time,the surface of the semiconductor layer is washed.

Then, an insulating film 613 is formed to cover the semiconductor layer.The insulating film 613 is formed to have a thickness of 1 to 200 nm bya plasma CVD method or a sputtering method. Preferably, after a singlelayer or a stacked layer of an insulating film including silicon isformed to have a thin thickness of 10 to 50 nm, a surface nitridingtreatment using plasma generated with a microwave is conducted. Theinsulating film 613 serves as a gate insulating film of a TFT to beformed later.

Next, a first conductive film with a thickness of 20 to 100 nm and asecond conductive film with a thickness of 100 to 400 nm are stackedover the insulating film 613. In this embodiment mode, a tantalumnitride film with a thickness of 50 nm and a tungsten film with athickness of 370 nm are sequentially stacked over the insulating film613, and patterned to form each gate electrode and each wiring by amethod shown below.

Here, TaN film and W film are stacked as a conductive film; however,there is no particular limitation. A single layer or a stacked layer ofan element selected from Ta, W, Ti, Mo, Al, or Cu or an alloy materialor a compound material mainly including such elements may be used. Asemiconductor film typified by a polycrystalline silicon film doped withan impurity element such as phosphorus, may also be used. In addition,the present invention is not limited to a two-layer structure. Forexample, a three-layer structure may be adopted in which a 50 nm thicktungsten film, an alloy film of aluminum and silicon (Al—Si) with athickness of 500 nm, and a 30 nm thick titanium nitride film aresequentially stacked.

An ICP (inductively coupled plasma) etching method may be used foretching the first conductive film and the second conductive film (afirst etching treatment and a second etching treatment). The ICP etchingmethod is used, and the etching conditions (the amount of an electricenergy applied to a coiled electrode, the amount of an electric energyapplied to an electrode on a substrate side, a temperature of theelectrode on the substrate side, and so on) are appropriately adjusted,so that a film can be etched to have a desired tapered shape.

The first etching treatment is conducted after a mask made of resist isformed. The first etching conditions include applying an RF (13.56 MHz)power of 700 W to a coiled electrode at a pressure of 1 Pa, employingCF₄, Cl₂, and O₂ for an etching gas, and setting the gas flow rate ratiothereof to 25:25:10 (sccm). The substrate side (sample stage) alsoreceives an RF power of 150 W (13.56 MHz) to apply a substantiallynegative self-bias voltage. The area (size) of the substrate sideelectrode is 12.5 cm×12.5 cm and the coiled electrode is a disc which is25 cm in diameter (here, a quartz disc provided with a coil). The W filmis etched under these first etching conditions to make the end portiontapered. Thereafter, the first etching conditions are switched to thesecond etching conditions without removing the resist mask 616. Thesecond etching conditions include using CF₄ and O₂ for an etching gas,setting the gas flow rate ratio thereof to 30:30 (sccm), and giving anRF (13.56 MHz) power of 500 W to a coiled electrode at a pressure of 1Pa to generate plasma for etching for about 30 seconds. The substrateside (sample stage) also receives an RF power of 20 W (13.56 MHz) toapply a substantially negative self-bias voltage. Under the secondetching conditions where a mixture of CF₄ and O₂ is used, the W film andthe TaN film are etched to almost the same degree. The first etchingconditions and the second etching conditions constitute the firstetching treatment.

FIG. 5A shows a cross section when the first etching treatment isfinished. At this stage, a gate electrode and a wiring are formed, inwhich the first conductive layer 614 a is a lower layer and the secondconductive layer 614 b is a lower layer. A terminal electrode in whichthe first conductive layer 615 a is a lower layer and the secondconductive layer 615 b is an upper layer, is formed.

Next, the second etching treatment is conducted with the resist mask 616kept in place. The third etching conditions include using CF₄ and Cl₂for an etching gas, setting the gas flow rate ratio thereof to 30:30(sccm), and giving an RF (13.56 MHz) power of 500 W to a coiledelectrode at a pressure of 1 Pa to generate plasma for etching for 60seconds. The substrate side (sample stage) also receives an RF power of20 W (13.56 MHz) to apply a substantially negative self-bias voltage.Then, the third etching conditions are switched to the fourth etchingconditions without removing the resist mask. The fourth etchingconditions include using CF₄, Cl₂, and O₂ for an etching gas, settingthe gas flow rate ratio thereof to 20:20:20 (sccm), and giving an RF(13.56 MHz) power of 500 W to a coiled electrode at a pressure of 1 Pato generate plasma for etching for about 20 seconds. The substrate side(sample stage) also receives an RF power of 20 W (13.56 MHz) to apply asubstantially negative self-bias voltage. The third etching conditionsand the fourth etching conditions constitute the second etchingtreatment. By this second etching treatment, third conductive layers 614c and 615 c are formed. Then, the mask made of resist is removed.

In the second etching treatment described above or in removing the maskmade of resist, a thin film including tungsten (W) (a thickness of about10 nm) is formed. A cross sectional view at this stage is shown in FIG.5B.

Thereafter, a first doping treatment for doping entirely is conductedusing a gate electrode as a mask, in order to add an impurity elementimparting an n-type conductivity to a semiconductor layer. An ion dopingmethod or an ion implantation method may be employed to conduct thefirst doping treatment. The conditions of the ion doping method are adose amount of 1.5×10¹³ atoms/cm² and an accelerating voltage of 50 to100 keV. As the impurity element imparting an n-type conductivity,phosphorus (P) or arsenic (As) is used typically. By this first dopingstep, doping is conducted through the insulating film 613 and the thinfilm including tungsten 617 to form a first impurity region (n⁻ region)618 in a self alignment manner. A cross sectional view at this stage isshown in FIG. 5C. Since the thin film including tungsten is provided, asemiconductor layer overlapped with the first conductive layer 614 a ishardly doped with the impurity element imparting an n-type conductivity.In addition, it is also possible that the impurity element imparting ann-type conductivity is prevented from being added to a portion under thefirst conductive layer 614 a by the existence of the thin film includingtungsten.

Next, the thin film including tungsten 617 is removed.

Then, after a mask made of resist 619 is formed, a second doping step isconducted to dope the semiconductor with an impurity element impartingan n-type conductivity at a high concentration. A cross sectional viewat this stage is shown in FIG. 6A. The mask 619 is provided to protect achannel forming region of the semiconductor layer forming a p-channelTFT of a pixel portion, and a periphery region thereof, and a part of ann-channel TFT in the pixel portion, and a channel forming region of asemiconductor layer forming a p-channel TFT in a driver circuit portionand a periphery region thereof.

Conditions of the ion doping method for the second doping step are adose amount of 1×10¹³ to 5×10¹⁵/cm² and an accelerating voltage of 60 to100 keV. Through this doping step, a second impurity region (n⁺ region)620 a and a third impurity region (n⁻ region) 620 b are formed. Thesecond impurity region 620 a includes a high concentration of an n typeimpurity which is added through the insulating film 613, and the thirdimpurity region (n⁻ region) 620 b is formed by doping through the firstconductive layer 614 a and the insulating film 613, and is overlappedwith first conductive layer 614 a. The n-channel TFT of the pixelportion is partially covered with a mask, and thus, the first impurityregion (n⁻ region) 618, which is not overlapped with the firstconductive layer 614 a, is formed between a channel forming region andthe second impurity region 620 a. In addition, in the n-channel TFT ofthe driver circuit portion, doping is made in a self alignment manner,so that a border between the third impurity region 620 b overlapping thefirst conductive layer 614 a and the second impurity region 620 a isaligned with an end portion of the first conductive layer 614 a.

Then, after removing the mask 619, a new mask made of resist 621 isformed, and a third doping step for doping the semiconductor with animpurity element imparting a p-type conductivity (typically boron) at ahigh concentration is conducted. A cross sectional view at this stage isshown in FIG. 6B. The mask 621 is provided to protect a channel formingregion of a semiconductor layer forming an n-channel TFT of the pixelportion, and a periphery region thereof, and a channel forming region ofa semiconductor layer forming an n-channel TFT in a driver circuitportion and a periphery region thereof.

The semiconductor layer is doped through the insulating film 613 by thethird doping step to form a fourth impurity region (p⁺ region) 622including a high concentration of a p-type impurity. In addition, thefourth impurity region 622 is a region (n⁻ region) doped with phosphorus(P) in the first doping step; however, the impurity element imparting ap-type conductivity is added at a concentration of 1.5 to 3 times asmuch as that of phosphorus (P) and thus, the conductivity is p-type.

After that, the resist mask is removed. Through the above describedsteps, an impurity region having an n-type or a p-type conductivity isformed in each semiconductor layer. A cross sectional view at this stageis shown in FIG. 6C.

Thereafter, an insulating film including hydrogen 640 a is formed by asputtering method, an LPCVD method, a plasma CVD method or the like, andthen, the impurity element added into the semiconductor layer isactivated and hydrogenated. As the insulating film including hydrogen640 a, a silicon nitride oxide film (SiNO film) obtained by a PCVDmethod is used. Here, the thickness of the insulating film includinghydrogen 640 a is 50 to 200 nm. In addition, gettering for reducingnickel in a channel formation region can also be performed at the sametime as activation, when the semiconductor film is crystallized by usinga metal element which promotes crystallization, typically, nickel. Notethat the insulating film containing hydrogen 640 a is a first interlayerinsulating film and contains silicon oxide.

Then, an inorganic insulating film 640 b to be a second layer of theinterlayer insulating film is formed by a sputtering method, an LPCVDmethod, a plasma CVD method or the like. As the inorganic insulatingfilm 640 b, a single layer or a stacked layer of an insulating film suchas a silicon oxide film, a silicon nitride film, or a silicon oxynitridefilm is used. Here, the thickness of the inorganic insulating film 640 bis 600 nm to 800 nm.

As one layer of the inorganic insulating film 640 b, a siloxane resinobtained by a coating method may be used. The siloxane resin correspondsto a resin including Si—O—Si bond. A skeleton structure of siloxane isformed from a bond of silicon (Si) and oxygen (O). As a substituent, anorganic group including at least hydrogen (for example, an alkyl group,or aromatic hydrocarbon) can be used. A fluoro group may also be used asa substituent. Further, an organic group including at least hydrogen anda fluoro group may be used as a substituent.

Then, a mask made of resist is formed using a photomask, and theinsulating films 640 a and 640 b and the insulating film 613 areselectively etched to form contact holes. Then, the mask made of resistis removed.

Then, after a metal film is stacked by a sputtering method, a mask madeof resist is formed using a photomask, and the stacked metal film isselectively etched to form electrodes 641 to 647 which serve as a sourceelectrode or a drain electrode of a TFT. The mask made of resist isremoved. Here, the stacked metal film has a three-layer structure of a100-nm-thick Ti film, a 350-nm-thick Al film including a slight amountof Si, and a 100-nm-thick Ti film.

In addition, line widths or positions for the side faces of theelectrodes 641 to 647 can be set appropriately such that the side facesthereof are not overlapped with the first conductive layer and the thirdconductive layer which are provided below.

Through the above mentioned steps, top gate type TFTs 636, 637, 638 and639 using a polysilicon film as an active layer are manufactured overthe same substrate, and a cross sectional view at this stage is shown inFIG. 6D.

The TFT 636 arranged in the driver circuit portion is an n-channel TFThaving a low concentration impurity region (also referred to as an LDDregion) which is overlapped with a gate electrode, and the TFT 637 is ap-channel TFT. In the driver circuit portion, the TFT 636 and the TFT637 are connected complementarily to form a CMOS circuit, and varioustypes of circuits can be realized.

In addition, the TFT 638 arranged in the pixel portion is an n-channelTFT having a plurality of channel forming regions in one TFT. The TFT638 is a multigate type TFT having a low concentration impurity region(also referred to as an LDD region) which is not overlapped with a gateelectrode. In addition, in the pixel portion, the TFT 639 is provided,which is electrically connected to a light-emitting element to be formedlater. Here, as the TFT 639, a single gate type p-channel TFT is shown;there is no particular limitation, and a multigate type TFT may be used.

Then, a first electrode 623, i.e., an anode (or a cathode) of an organiclight-emitting element is formed. As the first electrode 623, a singlelayer or a stacked layer of a material having a high work function, forexample, an element selected from Ni, W, Cr, Pt, Zn, Sn, In or Mo, or analloy material including such an element as its main component, forexample, TIN, TiSi_(x)N_(y), WSi_(x), WN_(x), WSi_(x)N_(y), or NbN, maybe formed to have a thickness of 100 to 800 nm.

Specifically, as the first electrode 623, a transparent conductive filmmade of a light-emitting conductive material may be used, for example,indium oxide including tungsten oxide, indium zinc oxide includingtungsten oxide, indium oxide including titanium oxide, indium tin oxideincluding titanium oxide or the like can be used. Needless to say,indium tin oxide (ITO), indium zinc oxide (IZO), indium tin oxide, withsilicon oxide added (ITSO) or the like can also be used.

Examples of a composition ratio in each light-transmitting conductivematerial are described. In indium oxide containing tungsten oxide,tungsten oxide may be 1.0 wt % and indium oxide may be 99.0 wt % in itscomposition ratio. In indium zinc oxide containing tungsten oxide,tungsten oxide may be 1.0 wt %, zinc oxide may be 0.5 wt %, and iridiumoxide may be 98.5 wt % in its composition ratio. In indium oxidecontaining titanium oxide, titanium oxide may be 1.0 to 5.0 wt % andindium oxide may be 99.0 to 95.0 wt % in its composition ratio. Inindium tin oxide (ITO), tin oxide may be 10.0 wt % and indium oxide maybe 90.0 wt % in its composition ratio. In indium zinc oxide (IZO), zincoxide may be 10.7 wt % and indium oxide may be 89.3 wt % in itscomposition ratio. Further, in indium tin oxide containing titaniumoxide, titanium oxide may be 5.0 wt %, tin oxide may be 10.0 wt %, andindium oxide may be 85.0 wt % in its composition ratio. The compositionratios as described above are just examples, and a composition ratio maybe set as is appropriate.

Next, an insulating film obtained by a coating method (for example, SiOxfilm including an alkyl group or an organic resin film) is patterned toform an insulator 629 (also referred to as a bank, a partition, abarrier, an embankment or the like) covering an end portion of the firstelectrode 623.

Then, a layer including an organic compound 624 is formed by anevaporation method or a coating method. Next, a second electrode 625,i.e., a cathode (or an anode) of the organic light-emitting element isformed. As the second electrode 625, an alloy such as MgAg, MgIn orAlLi, or a transparent conductive film (such as ITO) is used.

Then, a protective layer 626 is formed by an evaporation method or asputtering method. The protective layer 626 protects the secondelectrode 625. When light of the light-emitting element is extractedthrough the protective layer 626, a transparent material is preferablefor the protective layer 626. It is noted that the protective layer 626may not be provided, if not necessary.

Then, a sealing substrate 633 is attached by a sealant 628 to seal thelight-emitting element. In other words, in a light emitting displaydevice, the circumference of a display region is surrounded by thesealant and sealed with a pair of substrates. However, the interlayerinsulating film of the TAT is provided over the entire surface of thesubstrate. Therefore, when a pattern of the sealant is drawn inside acircumference edge of the interlayer insulating film, there is apossibility that moisture or an impurity might enter from a part of theinterlayer insulating film which is located outside the pattern of thesealant. Consequently, as for the circumference of the insulating filmused as the interlayer insulating film of the TFT, the sealant coversinside of the pattern of the sealant, preferably, the edge portion ofthe insulating film such that it overlaps a pattern of the sealant. Notethat a region surrounded by the sealant 628 is filled with a filler 627.Alternatively, the region surrounded by the sealant 628 is filled with adried inert gas.

Lastly, an FPC 632 is attached to a terminal electrode with ananisotropic conductive film 631 by a known method (FIG. 7). Atransparent conductive film obtained in the same step as the firstelectrode 623 is preferably used for a top layer of the terminalelectrode and is formed over the third conductive layer 615 c to serveas a layer of the terminal electrode formed simultaneously with a gatewiring.

Through the above steps, a pixel portion, a driver circuit, and aterminal portion are formed over one substrate.

In this embodiment mode, line widths or positions are set appropriatelysuch that side faces of the electrodes 641 to 647 are not overlappedwith side faces of the first conductive layer and the third conductivelayer which are arranged below, and the thickness of the insulator 629is assured. Therefore, it is possible to prevent the thickness frombeing partially thinned, and to prevent a short circuit in a portionwhere the electrodes 641 to 647 and the second electrode 625 areoverlapped.

In addition, in the light-emitting device, one surface or both surfacesof the light-emitting device may be used as a light-emitting displaysurface. In a case that the first electrode 623 and the second electrode625 are formed using transparent conductive films, light generated inthe light-emitting element is extracted on the opposite sides throughthe substrate 610 and the sealing substrate 633. In this case,transparent materials are preferably used for the sealing substrate 633or the filler 627.

In addition, in a case that the second electrode 625 is formed with ametal film, and the first electrode 623 is formed with a transparentconductive film, light generated in the light-emitting element isextracted through only the substrate 610, in other words, a bottomemission structure is obtained. In this case, it is not necessary to usea transparent material for the sealing substrate 633 or the filler 627.

When the first electrode 623 is formed with a metal film, and the secondelectrode 625 is formed with a transparent conductive film, lightgenerated in the light-emitting element is extracted only through thesealing substrate 633, in other words, a top emission structure isobtained. In this case, it is not necessary to use a transparentmaterial for the substrate 610.

Further, the materials for the first electrode 623 and the secondelectrode 625 need be selected in consideration of a work function.However, the first electrode and the second electrode can each be eitheran anode or a cathode depending on its pixel structure. When a polarityof a driving TFT is a p-channel type, it is preferable that the firstelectrode serves as an anode and the second electrode serves as acathode. When a polarity of the driving TFT is an n-channel type, it ispreferable that the first electrode serves as a cathode and the secondelectrode serves as an anode.

Moreover, in the light-emitting device, a driving method for displayingan image is not limited particularly, and a dot-sequential drivingmethod, a line-sequential driving method, or a frame sequential drivingmethod may be used, for example. The line-sequential driving method istypically employed, and a time division gray scale driving method or anarea gray scale driving method may be employed appropriately. Inaddition, a video signal to be inputted into a source line of thelight-emitting device may be an analog signal or a digital signal, and adriver circuit and the like may be designed appropriately according tothe video signal.

Further, light-emitting devices using digital video signals areclassified into ones in which video signals are inputted into a pixel ata constant voltage (CV), and ones in which video signals are inputtedinto a pixel at a constant current (CC). The light-emitting devices inwhich video signals are inputted into a pixel at a constant voltage (CV)are further classified into ones in which a signal is inputted to alight-emitting element at a constant voltage (CVCV), and ones in which asignal is inputted to a light-emitting element at a constant current(CVCC). The light-emitting devices in which video signals are inputtedinto a pixel at a constant current (CC) are classified into ones inwhich a constant voltage is applied to a light-emitting element as asignal (CCCV), and ones in which a constant current is applied to alight-emitting element as a signal (CCCC).

Furthermore, a protection circuit (such as a protection diode) may beprovided in the light-emitting device so as to prevent electrostaticdischarge damage.

This embodiment mode can be freely combined with any one of EmbodimentModes 1 to 3.

Embodiment Mode 5

Embodiment Mode 5 describes an example in which an FPC or a driver IC ismounted in a light-emitting display panel with reference to FIGS. 8A and8B.

FIG. 8A is a top view of a light-emitting device in which FPCs 1209 areattached to four terminal portions 1208, as an example. A pixel portion1202 including a light-emitting element and a TFT, a gate side drivercircuit 1203 including a TFT, and a source side driver circuit 1201including a TFT are formed over a substrate 1210. These circuits can beformed over one substrate when active layers of TFTs each are formedfrom a semiconductor film having a crystalline structure. Therefore, anEL display panel in which the system-on-panel is realized can bemanufactured.

Note that the portion of the substrate 1210 other than a contact portionis covered with a protective film, and a base layer containing aphotocatalytic substance is provided over the protective film.

Two connecting regions 1207 provided so as to sandwich the pixel portionare provided for contacting a second electrode of a light-emittingelement to a lower wiring. Note that a first electrode of thelight-emitting element is electrically connected to a TFT provided inthe pixel portion.

A sealing substrate 1204 is fixed to the substrate 1210 by a sealant1205 surrounding the pixel portion and the driver circuits and by afiller surrounded with the sealant. In addition, a structure in which afiller including a transparent drying agent is used may also beemployed. A drying agent may be disposed in a region which is notoverlapped with the pixel portion.

The structure shown in FIG. 8A is a preferred example of alight-emitting device of a relatively large size of XGA class (forexample, the opposite angle: 4.3 inches). FIG. 9B is an example ofemploying a COG mode which is suitable for a small size light-emittingdevice whose frame is narrowed (for example, the opposite angle: 1.5inches).

In FIG. 8B, a driver IC 1301 is mounted on a substrate 1310 and an FPC1309 is mounted on a terminal portion 1308 disposed at the end of thedriver IC. A plurality of the driver ICs 1301 to be mounted arepreferably formed over a rectangular substrate to be 300 to 1000 mm ormore on one side, from the view point of improving the productivity. Inother words, a plurality of circuit patterns having a driver circuitportion and an input-output terminal as a unit are preferably formedover a substrate and separated to take driver ICs. The driver IC may beformed to be rectangular with a longer side of 15 to 80 mm and a shorterside of 1 to 6 mm. Alternatively, the driver IC may have a side with alength corresponding to one side of a pixel region or a length in whichone side of a driving circuit is added to one side of the pixel portion.

The driver IC is superior to an IC chip in terms of external size, sinceit has a longer side. When a driver IC formed to be 15 to 80 mm on alonger side is used, the number of driver ICs to be required for beingmounted corresponding to the pixel portion is small, as compared withthe case of using IC chips, thereby improving the yield inmanufacturing. When a driver IC is formed over a glass substrate, theproductivity is not lost because there is no limitation on the shape ofa mother substrate. This is a great advantage, as compared with the caseof taking out an IC chip from a circular silicon wafer.

In addition, a TAB mode may be employed, and in that case, a pluralityof tapes are attached and a driver IC may be mounted on the tapes. As inthe case of the COG mode, a single driver IC may be mounted on a singletape. In this case, a metal piece or the like for fixing a driver IC ispreferably attached therewith in order to enhance the intensity.

A connecting region 1307 provided between a pixel portion 1302 and thedriving IC 1301 is provided for contacting a second electrode of alight-emitting element to a lower wiring. Note that the first electrodeof the light-emitting element is electrically connected to a TFTprovided for the pixel portion.

A sealing substrate 1304 is fixed on the substrate 1310 by a sealant1305 surrounding the pixel portion 1302 and by a filler surrounded withthe sealant.

When using an amorphous semiconductor film as an active layer of a TFTin the pixel portion, it is difficult to form a driver circuit over thesame substrate, and thus, the structure shown in FIG. 8B is employedeven when it has a large size.

The active matrix light emitting device is shown as an example of adisplay device here, and it is natural that the present invention can beapplied to an active matrix liquid crystal display device. In the activematrix liquid crystal display device, pixel electrodes arranged inmatrix are driven to display an image pattern on the screen.Specifically, a voltage is applied between a selected pixel electrodeand an opposite electrode corresponding to the pixel electrode, andthus, a liquid crystal between the pixel electrode provided in theelement substrate and the opposite electrode provided in the oppositesubstrate is modulated optically. The optical modulation can berecognized as an image pattern by an observer. The opposite substrateand the element substrate are disposed at an even interval apart and thespace therebetween is filled with a liquid crystal. The liquid crystalmaterial may be dropped under reduced pressure so that a bubble does notenter by the sealant having a closed pattern, and the substrates may bepasted onto each other. Alternatively, a dip method (pumping method) maybe employed in which the liquid crystal is injected using a capillaryphenomenon after providing a seal pattern having an opening portion andpasting the TFT substrate.

In addition, the present invention can be applied to a liquid crystaldisplay device with an optical shutter and a field sequential drivingsystem of blinking a backlight light source for three colors of RGB athigh speed, without a color filter.

As described above, by implementing the present invention, in otherwords, by using any structure or manufacturing method of EmbodimentModes 1 to 4, various electronic devices can be completed.

Embodiment Mode 6

As semiconductor devices and electronic devices according to the presentinvention, cameras such as video cameras or digital cameras, goggle-typedisplays (head mounted displays), navigation systems, audio reproductiondevices (such as car audio components, or audio components), personalcomputers such as laptop personal computers, game machines, mobileinformation terminals (mobile computers, cellular phones, mobile gamemachines, electronic books, and the like), image reproduction devicesprovided with a recording medium (specifically, devices which canreproduce content of a recording medium such as Digital Versatile Disk(DVD) and have a display for displaying the image), and the like can begiven. Specific examples of the electronic devices are shown in FIGS. 9Ato 9D and FIG. 10.

FIG. 9A shows a digital camera, which includes a main body 2101, adisplay portion 2102, an imaging portion, operation keys 2104, a shutter2106 and the like. FIG. 9A shows the digital camera seen from thedisplay portion 2102 side, and the imaging portion is not shown in FIG.9A. In accordance with the present invention, a highly reliable digitalcamera can be manufactured.

FIG. 9B shows a laptop personal computer including a main body 2201, acasing 2202, a display portion 2203, a keyboard 2204, an externalconnection port 2205, a pointing mouse 2206, and the like. In accordancewith the present invention, a highly reliable laptop personal computecan be manufactured.

FIG. 9C shows a portable image reproducing device provided with arecording medium (specifically a DVD player), which includes a main body2401, a casing 2402, a display portion A 2403, a display portion B 2404,a recording medium (such as a DVD) reading portion 2405, operation keys2406, a speaker portion 2407 and the like. The display portion A 2403mainly displays image information and the display portion B 2404 mainlydisplays character information. The category of such an imagereproducing device provided with a recording medium includes a home gamemachine and so on. In accordance with the present invention, a highlyreliable image reproducing device can be manufactured.

FIG. 9D shows a display device which includes a casing 1901, a support1902, a display portion 1903, a speaker portion 1904, a video inputterminal 1905 and the like. This display device is manufactured by usinga thin film transistor formed by a manufacturing method described inEmbodiment Modes described above for the display portion 1903 and adriver circuit. Liquid crystal display devices, light-emitting devicesand the like are given as examples of display devices. Specifically, alltypes of display devices for displaying information are included, forexample, display devices for computers, display devices for receivingtelevision broadcasting, and display devices for advertisement. Inaccordance with the present invention, a highly reliable display device,in particular, a large size display device having a large screen of 22to 50 inches, can be manufactured.

In the cellular phone shown in FIG. 10, a main body (A) 901 includingoperation switches 904, a microphone 905, and the like is connected witha hinge 910 to a main body (B) 902 including a display panel (A) 908, adisplay panel (B) 909, a speaker 906, and the like, and it is openableand closable by the hinge 910. The display panel (A) 908 and the displaypanel (B) 909 are placed in a casing 903 of the main body (B) 902together with a circuit board 907. Pixel portions of the display panel(A) 908 and the display panel (B) 909 are placed such that they arevisible through an opening formed in the casing 903.

As for the display panel (A) 908 and the display panel (B) 909, thespecifications such as the number of pixels can be appropriatelydetermined in accordance with the functions of the cellular phone 900.For example, the display panel (A) 908 and the display panel (B) 909 canbe combined as a main screen and a sub-screen, respectively.

In accordance with the present invention, a highly reliable mobileinformation terminal can be realized.

The cellular phone according to this embodiment mode can be changed invarious modes depending on functions or applications thereof. Forexample, it may be a camera-equipped cellular phone by implementing animaging element in the hinge 910. Even when the operation switches 904,the display panel (A) 908, and the display panel (B) 909 are placed inone casing, the above-described effect can be obtained. Further, asimilar effect can be obtained even when the structure of thisembodiment mode is applied to an information display terminal equippedwith a plurality of display portions.

As described above, various types of electronic devices can be completedby implementing the present invention, in other words, by using any onemanufacturing method or structure of Embodiment Modes 1 to 5.

The present invention is effective, since a short circuit inmanufacturing or after manufacturing a semiconductor device can beeffectively prevented.

The present application is based on Japanese Patent Application serialNo. 2005-141132 filed on May 13, 2005 in Japanese Patent Office, theentire contents of which are hereby incorporated by reference.

What is claimed is:
 1. A display device comprising: a transistor in apixel region over a substrate; a gate wiring layer electricallyconnected to the transistor; a first insulating film over the gatewiring layer; a source wiring layer over and in contact with the firstinsulating film, the source wiring layer electrically connected to thetransistor; a conductive layer over and in contact with the firstinsulating film, wherein the source wiring layer and the conductivelayer are formed of a same material; wherein the conductive layer iselectrically floating, wherein the gate wiring layer and the conductivelayer overlap with each other, and wherein the conductive layer does notoverlap a side edge of the gate wiring layer.
 2. The display deviceaccording to claim 1, wherein the material of the source wiring layerand the conductive layer comprises aluminum and titanium.
 3. The displaydevice according to claim 1, wherein the source wiring layer comprises amulti-layered film.
 4. The display device according to claim 1, whereinthe display device is a light emitting device.
 5. The display deviceaccording to claim 1, wherein the display device is a liquid crystaldevice.
 6. A display device comprising: a transistor in a first pixelregion over a substrate; a gate wiring layer electrically connected tothe transistor; a first insulating film over the gate wiring layer; asource wiring layer over the first insulating film, the source wiringlayer electrically connected to the transistor; a conductive layer overthe first insulating film, wherein the source wiring layer and theconductive layer are formed in a same step; wherein the conductive layeris electrically floating, wherein the gate wiring layer and theconductive layer overlap with each other, and wherein the conductivelayer does not overlap a side edge of the gate wiring layer.
 7. Thedisplay device according to claim 6, wherein the conductive layer islocated in a region between the first pixel region and a second pixelregion adjacent to the first pixel region.
 8. The display deviceaccording to claim 6, wherein the source wiring layer and the conductivelayer comprise aluminum and titanium.
 9. The display device according toclaim 6, wherein the source wiring layer comprises a multi-layered film.10. The display device according to claim 6, wherein the display deviceis a light emitting device.
 11. The display device according to claim 6,wherein the display device is a liquid crystal device.
 12. A displaydevice comprising: a transistor in a first pixel region over asubstrate; a gate wiring layer electrically connected to the transistor;a first insulating film over the gate wiring layer; a source wiringlayer over and in contact with the first insulating film, the sourcewiring layer electrically connected to the transistor; a conductivelayer over and in contact with the first insulating film, wherein thesource wiring layer and the conductive layer are formed of a samematerial; wherein the conductive layer is electrically floating, whereinthe gate wiring layer and the conductive layer overlap with each other,wherein the conductive layer does not overlap a side edge of the gatewiring layer, and wherein the conductive layer is located a regionbetween the first pixel region and a second pixel region adjacent to thefirst pixel region.
 13. The display device according to claim 12,wherein the source wiring layer and the conductive layer are formed in asame step.
 14. The display device according to claim 12, wherein thematerial of the source wiring layer and the conductive layer comprisesaluminum and titanium.
 15. The display device according to claim 12,wherein the source wiring layer comprises a multi-layered film.
 16. Thedisplay device according to claim 12, wherein the display device is alight emitting device.
 17. The display device according to claim 12,wherein the display device is a liquid crystal device.
 18. A displaydevice comprising: a transistor in a pixel region over a substrate; agate wiring layer electrically connected to the transistor; a firstinsulating film over the gate wiring layer; a source wiring layer overthe first insulating film, the source wiring layer electricallyconnected to the transistor; a conductive layer over the firstinsulating film, wherein the source wiring layer and the conductivelayer are formed of a same material; wherein the conductive layer iselectrically floating, wherein the gate wiring layer and the conductivelayer overlap with each other, and wherein the conductive layer does notoverlap a side edge of the gate wiring layer.
 19. The display deviceaccording to claim 18, wherein the source wiring layer and theconductive layer are formed in a same step.
 20. The display deviceaccording to claim 18, wherein the material of the source wiring layerand the conductive layer comprises aluminum and titanium.
 21. Thedisplay device according to claim 18, wherein the source wiring layercomprises a multi-layered film.
 22. The display device according toclaim 18, wherein the display device is a light emitting device.
 23. Thedisplay device according to claim 18, wherein the display device is aliquid crystal device.
 24. A display device comprising: a transistor ina first pixel region over a substrate; a gate wiring layer electricallyconnected to the transistor; a first insulating film over the gatewiring layer; a source wiring layer over the first insulating film, thesource wiring layer electrically connected to the transistor; aconductive layer over the first insulating film, wherein the sourcewiring layer and the conductive layer are formed of a same material;wherein the conductive layer is electrically floating, wherein the gatewiring layer and the conductive layer overlap with each other, whereinthe conductive layer does not overlap a side edge of the gate wiringlayer, and wherein the conductive layer is located a region between thefirst pixel region and a second pixel region adjacent to the first pixelregion.
 25. The display device according to claim 24, wherein the sourcewiring layer and the conductive layer are formed in a same step.
 26. Thedisplay device according to claim 24, wherein the material of the sourcewiring layer and the conductive layer comprises aluminum and titanium.27. The display device according to claim 24, wherein the source wiringlayer comprises a multi-layered film.
 28. The display device accordingto claim 24, wherein the display device is a light emitting device. 29.The display device according to claim 24, wherein the display device isa liquid crystal device.